Some of the drug and macromolecules are poorly absorbed across the mucosal membrane or those that are sparingly/slowly soluble resulting in the fact that during limited time they remain in the gastrointestinal tract, enough of them is not released or absorbed and major portion passes out unabsorbed. One of the greatest challenge to the scientists is drug delivery of such molecules which show poor bioavailability as limited amount of the dose reaches the plasma in a specified period. Low bioavailability leads to variation in the drug absorption amongst the patients and become very difficult to administer the effective dosage. Hence, it has been a long awaited requirement of the drug delivery scientists to enhance the bioavailability of the such orally administered drugs. It was thought that a carrier which can deliver drug in intact form at target site, stays there for prolonged time and increases the permeability of the mucosal membrane to achieve unhampered and better absorption of the drug shall be a remedy, provided the carrier is safe and does not affect the properties of the mucosal epithelium. Acyclovir, one of the subject matters of present invention is a drug in this category: poorly water soluble, has poor and variable oral bioavailability (10-20%), the elimination half-life of aciclovir is approximately 3 hours, is renally excreted, partly by glomerular filtration and partly by tubular secretion.
The present invention deals with carriers, including but not limited to polymers like chitosan (and its derivatives not limited to Thiolated chitosan, Trimethyl chitosan, hypermellose, polyethylene oxide, CARBOPOL®, sodium alginate, sodium carboxymethyl cellulose, xanthan gum and similar products, derivatives of these polymers, their various combinations and the like which are mucoadhesive, swellable and which increases the G.I. retention, bioavailability of the drug during the delivery.